Field of the Invention
The present invention concerns methods of extracting petroleum. In particular, the invention concerns an improved method of stimulating fluid flow in a well bore using a fracturing tool assembly with an interiorly disposed dump valve.
Description of the Prior Art
Petroleum production from a well bore is often enhanced by a process that is characterized as fracturing or fracking. According to the general principles of fracking, the fracturing process induces increased fluid flow from the well bore production face by generating additional cracks and fissures into the zone surrounding the well bore wall. The objective of creating cracks and fissures in the fracking zone is an increase in the production face area. This increased production area facilitates flow of a greater volume of petroleum fluid into the well production flow stream than would otherwise occur from the penetration area provided by the original borehole.
Among the known methods of creating or enlarging such cracks and fissures into a fluid production zone is that of forcing liquid into the formation under extremely high pressure. Mixed with the high pressure fracturing liquid are particulates such as coarse sand or fine gravel known as proppants. These proppants have the function of holding open and maintaining the permeability of zone fractures. A zone is fluidly isolated from other zones in the well bore by a suitable sealing means such as inflatable packers so that the fluid, including the proppant, is forced into the well bore thereby creating fissures which stimulate the flow of oil.
A problem occurs when fracking multiple zones within the same well bore. Unloading or releasing the fracking liquid when moving from one zone to the next is harmful to the tool set. The fracking liquid is highly abrasive and since prior art tools generally release the liquid from openings positioned on the side of the tool set the tools are damaged over time from the effects of the abrasive fluid contacting the portions of the tool below the release point.